Various devices can be installed in a well traversing a hydrocarbon-bearing subterranean formation. One example is a perforating assembly, such as a tubing conveyed perforating (“TCP”) gun. A TCP gun can be conveyed using tubing, drillpipe or coiled tubing and include explosive charges or other mechanisms that can perforate oil and gas wells.
A perforating assembly can include a safeguard mechanism to prevent the perforating assembly from firing unintentionally. For example, the safeguard mechanism can provide an interrupt to deactivate the firing mechanism by preventing a charge train from causing a charge to explode. The safeguard mechanism can activate the firing mechanism after the perforating assembly is run downhole. The safeguard mechanism can activate the firing mechanism in response to the temperature in the wellbore causing a solder to melt, resulting in a contact to allow the charge train to travel through the perforating assembly. Other safeguard mechanisms can activate the firing mechanism in response to high pressure in the wellbore.
Although these safeguard mechanisms are effective, some wellbores include long, shallow, and/or horizontal bores in which the difference in temperature and pressure with respect to the surface is small. The temperature or pressure threshold at which these safeguard mechanisms activate the firing mechanism may be closer to a theoretical possible range of temperatures or pressures at the surface.
Furthermore, these safeguard mechanisms may not include a way to deactivate the firing mechanism if and when the perforating assembly is retrieved from the wellbore back to the surface.
Accordingly, assemblies and devices are desirable that can provide additional safety for perforating assemblies run downhole and/or brought back to the surface.